• 한국수학교육학회지시리즈D:수학교육연구
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• 제19권3호
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• pp.155-174
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• 2015

The goal of this study was to examine the three components of a laboratory class cycle that empowered teachers to change their teaching practices. Six teachers and their administrator in an elementary school in the southeastern United States participated in the study. All the teachers were interviewed, and their mathematics lessons were observed at the end of each cycle of laboratory classes. The study revealed how planning, observing, and critiquing mathematics lessons as a team assisted the teachers' learning and teaching. We identified opportunities for the teachers to experiment with different teaching approaches, and we found that support from the team and from the school were key factors for the laboratory class cycle to function effectively.

• ETRI Journal
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• 제36권6호
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• pp.924-930
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• 2014

This paper presents a $0.13{\mu}m$ CMOS 3-level envelope delta-sigma modulation (EDSM) RF signal generator, which synthesizes a 2.6 GHz-centered fully symmetrical 3-level EDSM signal for high-efficiency power amplifier architectures. It consists of an I-Q phase modulator, a Class B wideband buffer, an up-conversion mixer, a D2S, and a Class AB wideband drive amplifier. To preserve fast phase transition in the 3-state envelope level, the wideband buffer has an RLC load and the driver amplifier uses a second-order BPF as its load to provide enough bandwidth. To achieve an accurate 3-state envelope level in the up-mixer output, the LO bias level is optimized. The I-Q phase modulator adopts a modified quadrature passive mixer topology and mitigates the I-Q crosstalk problem using a 50% duty cycle in LO clocks. The fabricated chip provides an average output power of -1.5 dBm and an error vector magnitude (EVM) of 3.89% for 3GPP LTE 64 QAM input signals with a channel bandwidth of 10/20 MHz, as well as consuming 60 mW for both channels from a 1.2 V/2.5 V supply voltage.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.522-531
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• 2021

We describe a new deep learning model - Convolutional eXtreme Gradient Boosting (ConvXGB) for classification problems based on convolutional neural nets and Chen et al.'s XGBoost. As well as image data, ConvXGB also supports the general classification problems, with a data preprocessing module. ConvXGB consists of several stacked convolutional layers to learn the features of the input and is able to learn features automatically, followed by XGBoost in the last layer for predicting the class labels. The ConvXGB model is simplified by reducing the number of parameters under appropriate conditions, since it is not necessary re-adjust the weight values in a back propagation cycle. Experiments on several data sets from UCL Repository, including images and general data sets, showed that our model handled the classification problems, for all the tested data sets, slightly better than CNN and XGBoost alone and was sometimes significantly better.

• Clinical and Experimental Pediatrics
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• 제49권11호
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• pp.1125-1139
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• 2006

In 1991, the Ministry of Health & Social affairs adopted a nationwide service program for neonatal screening of phenylketonuria, galactosemia, maple syrup urine disease, homocystinuria, histidinemia & congenital hypothyroidism for newborns delivered from low class pregnant women registered in health centers. Government decreased the test items from six to two, PKU & congenital hypothyroidism to increase test numbers with same budget from 1995. Government decided to test PKU & hypothyroidism for all newborns from 1997. 78 laboratories wanted to participate for neonatal screening test in 1999. Government didn't decide laboratory center for a certain district and placed responsibility on free competition. Government are planning to test 573,000 newborns from 1998, Government decided to screen 6 items PKU, congenital hypothyroidism, maple syrup urine disese, homocystinuria, galactosemia and congenital adrenal hyperplasia from 2006. 17 laboratores are participating now. The cost of screening test is supported by both the federal government and local government on a 40-60 basis. In case a patient with an inherited metabolic disease is diagnosed by screening of government program, special milk is provided at government's expense. Interlaboratory quality control was started 6 times a year from 1994. According to the government project, 3,707,773 newborns were screened. 86 PKU, 718 congenital hypothyroidism were detected. So incidence of PKU is 1/43,114 and congenital hypothyroidism is 1/4,612. Maeil dairy company produced new special formula for PKU, MMA and PA, MSUD, urea cycle disorder, homocystinuria, isovaleric acidemia from Oct. 1999. The cost benefit of performing screening procedures coupled with treatment has been estimated to be as high as 1.77 times in PKU, 11.11 times in congenital hypothyroidism than cost without screening. We are trying to increase the budget to test all newborns for Tandem mass sereening & Wilson disease from 2008. Now it is a very important problem to decrease laboratory numbers of neonatal screening in Korea. So we are considering 4-5 central laboratories which cover all newborns and are equipped with tandem mass spectrometer & enzyme immunoassay for TSH, 17OHP & enzyme colorimetric assay for galactose.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.20-20
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• 2017

Plant genomes include heterochromatic loci that consist of repetitive sequences and transposable elements. LTR retrotransposon is the major class of transposons in advanced plants in terms of proportion in plant genome. The elements contribute not only to genome size but also to genome stability and gene expression. A number of cases have been reported transposon insertions near genic regions affect crop traits such as fruit pigments, stress tolerance, and yields. Functional LTR retrotransposons produce extrachromosomal DNA from genomic RNA by reverse transcription that takes place within virus-like-particles (VLPs). DECREASED DNA METHYLATION 1 (DDM1) plays important roles in maintaining DNA methylation of heterochromatin affecting all sequence contexts, CG, CHG, and CHH. Previous studies showed that ddm1 mutant exhibits massive transcription of retrotransposons in Arabidopsis, but only few of them were able to create new insertions into the genome. RNA-dependent RNA POLYMERASE 6 (RDR6) is known to function in restricting accumulation of transposon RNA by processing the transcripts into 21-22 nt epigenetically activated small interfering RNA (easiRNA). We purified VLPs and sequence cDNA to identify functional LTR retrotransposons in Arabidopsis ddm1 and ddm1rdr6 plants. Over 20 LTR copia and gypsy families were detected in ddm1 and ddm1rdr6 sequencing libraries and most of them were not reported for mobility. In ddm1rdr6, short fragments of ATHILA gypsy elements were detected. It suggests easiRNAs might regulate reverse transcription steps. The highest enriched element among transposon loci was previously characterized EVADE element. It has been reported that active EVADE element is more efficiently silenced through female germline than male germline. By genetic analyses, we found ddm1 and rdr6 mutation affect maternal silencing of active EVADE elements. DDM1-GFP protein accumulated in megaspore mother cell but was not found in mature egg cell. The fusion protein was also found in early embryo and maternal DDM1-GFP allele was more dominantly expressed in the embryo. We observed localization of DDM1-GFP in Arabidopsis and DDM1-YFP in maize and found the proteins accumulated in dividing zone of root tips. Currently we are looking at cell cycle dependency of DDM1 expression using maize system. Among 10 AGO proteins in Arabidopsis, AGO9 is specifically expressed in egg cell and shoot meristematic cells. In addition, mutation of AGO9 and RDR6 caused failure in maternal silencing, implying 21-22 nt easiRNA pathway is important for retrotransposon silencing in female gametophyte or/and early embryo. On the other hand, canonical 24 nt sRNA-directed DNA methylation (RdDM) pathways did not contribute to maternal silencing as confirmed by this study. Heat-activated LTR retrotransposon, ONSEN, was not silenced by DDM1 but the silencing mechanisms require RdDM pathways in somatic cells. We will propose distinct mechanisms of LTR retrotransposons in germline and somatic stages.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.97-97
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• 2017

Plant genomes include heterochromatic loci that consist of repetitive sequences and transposable elements. LTR retrotransposon is the major class of transposons in advanced plants in terms of proportion in plant genome. The elements contribute not only to genome size but also to genome stability and gene expression. A number of cases have been reported transposon insertions near genic regions affect crop traits such as fruit pigments, stress tolerance, and yields. Functional LTR retrotransposons produce extrachromosomal DNA from genomic RNA by reverse transcription that takes place within virus-like-particles (VLPs). DECREASED DNA METHYLATION 1 (DDM1) plays important roles in maintaining DNA methylation of heterochromatin affecting all sequence contexts, CG, CHG, and CHH. Previous studies showed that ddm1 mutant exhibits massive transcription of retrotransposons in Arabidopsis, but only few of them were able to create new insertions into the genome. RNA-dependent RNA POLYMERASE 6 (RDR6) is known to function in restricting accumulation of transposon RNA by processing the transcripts into 21-22 nt epigenetically activated small interfering RNA (easiRNA). We purified VLPs and sequence cDNA to identify functional LTR retrotransposons in Arabidopsis ddm1 and ddm1rdr6 plants. Over 20 LTR copia and gypsy families were detected in ddm1 and ddm1rdr6 sequencing libraries and most of them were not reported for mobility. In ddm1rdr6, short fragments of ATHILA gypsy elements were detected. It suggests easiRNAs might regulate reverse transcription steps. The highest enriched element among transposon loci was previously characterized EVADE element. It has been reported that active EVADE element is more efficiently silenced through female germline than male germline. By genetic analyses, we found ddm1 and rdr6 mutation affect maternal silencing of active EVADE elements. DDM1-GFP protein accumulated in megaspore mother cell but was not found in mature egg cell. The fusion protein was also found in early embryo and maternal DDM1-GFP allele was more dominantly expressed in the embryo. We observed localization of DDM1-GFP in Arabidopsis and DDM1-YFP in maize and found the proteins accumulated in dividing zone of root tips. Currently we are looking at cell cycle dependency of DDM1 expression using maize system. Among 10 AGO proteins in Arabidopsis, AGO9 is specifically expressed in egg cell and shoot meristematic cells. In addition, mutation of AGO9 and RDR6 caused failure in maternal silencing, implying 21-22 nt easiRNA pathway is important for retrotransposon silencing in female gametophyte or/and early embryo. On the other hand, canonical 24 nt sRNA-directed DNA methylation (RdDM) pathways did not contribute to maternal silencing as confirmed by this study. Heat-activated LTR retrotransposon, ONSEN, was not silenced by DDM1 but the silencing mechanisms require RdDM pathways in somatic cells. We will propose distinct mechanisms of LTR retrotransposons in germline and somatic stages.

• 대한원격탐사학회지
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• 제36권6_1호
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• pp.1339-1348
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• 2020

식물성플랑크톤은 영양염, 광합성, 탄소순환 등의 측면에서 해양의 생태계를 제어하는데, 해양 환경에 미치는 영향의 정도는 식물성플랑크톤의 크기에 좌우된다. 원격탐사 기술을 기반으로 해양의 식물성플랑크톤 크기 별 생체량을 식별하려는 많은 연구가 있었으며, 그 중 가장 성공적인 접근법 중 하나는 식물성플랑크톤의 크기를 세 등급(micro-plankton;> 20 ㎛, nano-; 2-20 ㎛ 및 pico-; <2 ㎛)으로 구분하여 각 그룹별 엽록소 농도를 추정하는 삼성분 모델(three-component model)이다. 이 연구에서는 동해에서 식물성플랑크톤의 크기 별 생체량 분포를 추정하기 위한 GOCI 자료의 활용 가능성에 대해 검토하였다. 각 크기 별 엽록소 농도(CHL)를 도출하기 위해, 연구지역에서 수 년 동안 수집된 식물성플랑크톤 색소자료를 기반으로 회귀분석을 통해 삼성분 모델의 계수를 산출하였다. 새롭게 산출된 삼성분 모델을 시간 별 GOCI 기반 엽록소 농도 이미지에 적용하여, 전체 엽록소 농도 중 각 식물성플랑크톤 크기 별 생체량이 차지하는 비율을 산출하였다. 또한, 이 결과를 이용하여 동해에서 2013년 여름 대규모 적조가 발생한 시기의 크기 별 엽록소-a 농도 분포를 분석하였다.

• 공업화학
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• 제25권1호
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• pp.1-13
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• 2014

리튬이온 배터리는 전기화학 에너지 저장 및 변환 기기에서 가장 높은 수준의 기술력을 기반으로 개발된 셀이며, 여전히 높은 에너지 밀도와 충방전 안정성이 높아서 가장 매력적인 배터리의 부류로서 평가받고 있다. 최근 급속한 대형 에너지 저장 응용시스템의 개발이 이루어지면서 기존의 그래파이트 전극을 대체하기 위한 새로운 음극물질의 개발이 요구되고 있다. 게르마늄과 실리콘은 이론적 에너지 용량이 높아서 다음 세대 리튬 배터리의 적합한 물질로 평가받고 있으며, 특히 게르마늄은 실리콘에 비해 충방전에 따른 부피변화가 상대적으로 적고, 리튬이온의 동력학 거동이 용이하며, 높은 전기전도도 특성이 있다. 본 총설에서는 우선 리튬이온 배터리의 기본 원리를 소개하고, 배터리 특성을 최대한 발휘할 수 있는 이상적인 음극 물질의 구조와 특성을 살펴보고자 한다. 다음 세대 음극물질로 고려되고 있는 게르마늄 복합체가 어떻게 현재의 리튬 배터리를 개선할 수 있을지를 논의하려고 한다. 그리고 최근 시도되고 있는 연구동향에 대한 소개를 끝으로 리튬이온 배터리의 고에너지 밀도화에 대한 참고문헌이 될 수 있기를 바란다.

• 생태와환경
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• 제36권4호통권105호
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• pp.403-412
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• 2003

전남 주암호에서의 식물플랑크톤 동태를 파악하기 위해 2003년 2월부터 10월까지 식물플랑크톤생체량 (클로로필 a)의 크기별 시 ${\cdot}$ 공간적 변동과 제반 환경요인에 대해 조사하였다. 본 논문에서는 주암호와 같은 담수호에서 식물플랑크톤의 크기 구조가 계절적, 공간적으로 어떻게 변화하고 그러한 변화 속에서 물리적 요인들이 어떤 영향을 미치는지 회귀분석을 통해 파악하고자 하였다. 식물플랑크톤 (클로로필 a)은 세 그룹 즉, 대형 (micro-size > 20 ${\mu}m$), 소형 (nano-size 3-20 ${\mu}m$) 마지막으로 초소형 (pico-size, < 3 ${\mu}m$)으로 구분했다. 물리적 특성 파악을 위해 수온, 광소멸계수, PAR (photosynthetically active radiation), 수중 탁도등도 동시에 측정하였다. 최대치의 클로로필 a 는 2003년 하류지역에서는 4월에 상류지역에서는 10월에 발생하였다. 식물플랑크톤의 대번성기에는 대부분 세포크기가 큰 대형 (micro-size)식물플랑크톤이 우세하였다. 주암호의 크기별 식물플랑크톤의 변동에 영향을 미칠 수 있는 물리적 특성들에 대해 논의하였다.